A bundle fiber obtained by bundling a large number of optical fibers effectively has a large core area, being able to make a large quantity of light incident or transmit a large quantity of light. Accordingly, bundle fibers are used in various fields such as an industrial field, a medical field, and a field of analysis.
Examples of a bundle fiber include not only a light transmitting bundle fiber and a light receiving bundle fiber which transmit light merely in one direction but also a transmitting-receiving bundle fiber which transmits light in both directions. Compared to the use of an independent light transmitting bundle fiber and an independent light receiving bundle fiber, easier installation and a smaller installation space are required advantageously in the use of a transmitting-receiving bundle fiber.
The length of a bundle fiber is determined in accordance with the application thereof, and approximately 10 in of length of bundle fiber is sometimes required depending on the application. Such long bundle fiber exhibits such problem that handling thereof is complicated and the whole bundle fiber has to be exchanged when a damage or a failure occurs.
In order to avoid such problem, such method is conceivable that a bundle fiber is separated into some parts and used in a connected manner, for example, but positioning of respectively-corresponding optical fibers is impossible in connection of those bundle fibers, so that large increase of optical connection loss is undeniable.
It is necessary to use an optical connector which enables positioning of each optical fiber so as to connect optical fibers to each other with low loss, and an optical signal connection member which includes such optical connectors on both ends thereof is described in Patent Literature 1.
FIGS. 1A to 1C illustrate an aspect of the optical signal connection member described in Patent Literature 1. As illustrated in FIG. 1C, this optical signal connection member is composed of a first optical fiber sheet 11, a second optical fiber sheet 12, and a first connector 13 and a second connector 14 which are respectively attached to one ends and the other ends of the first optical fiber sheet 11 and the second optical fiber sheet 12. FIGS. 1A and 1B respectively illustrate the configuration of the first optical fiber sheet 11 and the configuration of the second optical fiber sheet 12, and 15 in FIGS. 1A and 1B denotes optical fibers. The first optical fiber sheet 11 and the second optical fiber sheet 12 respectively include curve parts 11a and 12a and directions of the curve of the curve parts 11a and 12a are opposite to each other.
On the left side of FIG. 1C, the first optical fiber sheet 11 and the second optical fiber sheet 12 are disposed so that the first optical fiber sheet 11 is laminated on the second optical fiber sheet 12 and the optical fibers 15 protruding from each end portion are inserted to be attached into holes of a ferrule of the first connector 13. A window 16 is seen on the upper surface of the first connector 13.
On the other hand, on the right side of FIG. 1C, the second optical fiber sheet 12 is positioned on the first optical fiber sheet 11 and thus, the lamination order is different from that of the left side of FIG. 1C. The optical fibers 15 protruding from each end portion are attached to the second connector 14 in a similar manner to the first connector 13. A window of the second connector 14 is positioned on the lower side.
The optical signal connection member having the configuration as the one described above is used as a relay cable between two bundle fibers, for example, and connectors to be respectively connected with the first connector 13 and the second connector 14 are attached to connection ends of each bundle fiber, being able to realize separate bundle fibers without increase of optical connection loss and without the use of a single long bundle fiber. Here, the arrangements of the optical fibers 15 are same as each other when the tip end surfaces are observed in a manner that the connectors 13 and 14 provided on both ends are positioned so that their surfaces having the windows 16 face the upper side, in the optical signal connection member illustrated in FIG. 1C.